1. Field of Invention
The present invention relates, generally, to shift actuators for operatively engaging and disengaging associated gear sets, and more specifically, to spring loaded shift actuator having a retaining mechanism for controlling shifts in transmissions, transfer cases and other disconnect systems for four-wheel drive couplings and the like.
2. Description of the Related Art
In both early and many modern transmissions and transfer cases, shifts between various speed ranges and operating conditions are often achieved by a manual linkage controlled by the vehicle operator. Frequently, such linkages include one, or a plurality of, parallel shift rails which may be translated out of a center, neutral position to a forward or rearward position to select a given gear or operating mode.
In contemporary consumer products such as sport utility vehicles and light and medium duty trucks, gear range and operating modes in transfer cases are now more commonly selected through the agency of an electric-mechanical, pneumatic of hydraulic operator. A variety of drive assemblies and intermediate linkages have been developed to achieve range selection and transfer case operating more, e.g. lock up of a viscous clutch, a differential or modulating clutch to directly couple the primary and secondary drive lines.
In addition, it is known in the automotive industry to equip power transfer assemblies (ei.e. manual transmission, manual transmissions, transfer cases, etc.) with a shift system having spring shift devices for completing a delayed gear or mode shift once speed synchronization or a torque brake occurs. In most of the systems know in the related art, a pair of springs are used to provide a by-direction preload function for effectuating coupling of a dog-type shift sleeve with a desired gear set.
The devices known in the related art known as referenced above represent equally varying levels of complexity, sophistication, reliability and cost. Often times, a sophisticated system which provides rapid and precise selection of gears or operating modes falls short from a reliability standpoint. On the other hand, simple systems often do not provide positive, accurate or repeatable shifts although they are reliable.
Thus, there remains a need in the art for a shift actuator that is fast, efficient, relatively uncomplicated and inexpensive to manufacture.